1. Field of the Invention
The present invention relates to a color detection circuit used for detecting a desired color from a video signal to perform image processing.
2. Description of the Related Art
Skin-detail is a heretofore known technique wherein a desired color is detected from a video signal imaged with a television camera and image processing is performed. The skin-detail is performed by detecting a skin-color area from the video signal imaged and controlling an outline enhancement signal. According to the technique of the skin-detail, it is possible to show a face of a person more favorable.
This technique has become more important because of a recent development of high definition imaging of video apparatuses including the television camera. That is, since the number of pixels constituting a screen is increased for the high definition imaging and a video image has a higher resolution, it is required to prevent undesired portions from standing out.
In addition, there is a color corrector for detecting the desired color and performing the image processing. The color corrector performs color correction processing to a color and a color area to be detected. By performing the color correction processing using the color corrector, it is possible, for example, to make a color departing from a specified color system put in a range of the color system. Moreover, for usages of monitoring and examination of the video image, there have been a variety of applications of the color corrector such as one for facilitating determination and judgment of a certain object by changing the color to be detected into the desired color.
As a conventional skin-color detection circuit, a technique is suggested where an IQ signal is generated from an RGB video signal obtained from the television camera and a skin-color judgment is performed based on the IQ signal (see Japanese Patent No. 2986625, for example).
Incidentally, a color has a property of changing its density remarkably according to the brightness of an environment. For example, when imaging a face of a person, a color of the face of the person in the image, which should stay in the original color, differs dramatically according to a small change of a direction from which the light illuminates the face.
However, a skin-color detection circuit and an imaging device suggested in the above Japanese Patent No. 2986625 performs color detection based only on the IQ signal, that is, a color difference in a two-dimensional plane. Thus, the skin-color detection circuit and the imaging device cannot accurately control detection based on a luminance difference.
Since the television camera for broadcasting, in particular, is often used under special circumstances which are different from the usual surrounding environment, it is necessary to consider controlling in relation to a luminance direction. In addition, it is difficult to detect a desired color range by simply specifying a detection region because people's skin colors vary dramatically among individuals by race, for example. It is thus necessary to consider a method for controlling the detection region as well.